Wheelchairs having many different features have been long known, including height adjustable wheelchairs. However, a significant problem with such height adjustable wheelchairs resides in the lift mechanism, which typically is large and bulky so as to be able to lift people of all sizes. The convention drive mechanism generally includes a screw that is turned by a motor so as to raise and lower the chair. However, turning the screw requires a relatively large motor with sufficient horsepower. The extent of the lift is also limited by the drive train required to turn the screw. The bulky drive train also occupies substantial space in the wheelchair, which precludes the chair from being used in certain situations, for example, over a toilet for use of the toilet by a person in the chair. The construction of the chair and lift mechanism also makes the chair heavy, and therefore more difficult to maneuver.
Accordingly, a primary objective of the present invention is the provision of an improved wheelchair having a simple and compact lift mechanism for adjusting the height of the chair.
Another objective of the present invention is the provision of a wheelchair having a seat which is height adjustable and tiltable.
A further objective of the present invention is the provision of a wheelchair having a seat and upper frame member that can be raised to the level of a bed to facilitate transfer of a person between the bed and the wheelchair.
A further objective of the present invention is the provision of a height adjustable wheelchair having a U-shaped frame to allow the chair to be positioned over a toilet for use of the toilet by a person on the chair.
Another objective of the present invention is the provision of a wheelchair having a seat that can be tilted forwardly and raised so as to facilitate a person""s entry and exit to and from the chair.
Another objective of the present invention is the provision of a wheelchair movable between a lowered position wherein a person""s legs will fit beneath a table and a raised position wherein a person can reach objects on a shelf above a countertop.
Still another objective of the present invention is a provision of a wheelchair having caster wheels which automatically caster to provide an enlarged footprint when the chair is moved in one direction and a reduced footprint when the chair is moved in the opposite direction.
Still another objective of the present invention is the provision of a height adjustable wheelchair that is economical to manufacture, lightweight, and stable and safe in use.
These and other objectives will become apparent from the following description of the invention.
The height adjustable wheelchair of the present invention includes a lower frame member and an upper frame member. A seat has a forward edge pivotally connected to the upper frame member and a rearward edge releasably latched to the upper frame member. A lift mechanism extends between the lower frame member and the seat so as to raise the seat and upper frame member when the seat is latched to the upper frame member, and to tilt the seat forwardly when the seat is unlatched from the upper frame member.
The lift mechanism includes a pair of hollow tubes mounted on each side of the lower frame member in a vertical orientation. A threaded shaft or screw is threadably received within the tubes. A drive motor is operatively connected to each of the tubes via belts or chains so as to rotate the tubes, and thereby extend or retract the threaded shafts so as to raise or lower the seat, respectively. The wheelchair includes armrests with one or more switches for controlling actuation of the motor. The motor is powered by a battery mounted in the lower frame member.
The rear of the seat can also be unlatched from the upper frame member, such that the seat can be tilted forwardly when the screws are extended, thereby facilitating ingress and egress of a person to and from the chair.
Scissor-type braces are provided on the opposite sides and on the front of the wheelchair, and extend between the upper and lower frame members, so as to provide stability, particularly when the seat is moved to a raised position.
The lower frame member is U-shaped, with opposite side, a connected front and an open back, such that the wheelchair can be backed into position over a toilet. The seat includes a pair of cushions that can be opened laterally to allow a person sitting in the chair to use the toilet.
The wheelchair includes four wheels, with the two rear wheels preferably being caster wheels. When the wheelchair is rolled in a forward direction, the caster wheels caster to a rearward position so as to provide an enlarged footprint for the wheelchair, thereby enhancing stability. When the wheelchair is rolled rearwardly, the caster wheels caster to a forward position, thereby reducing the footprint, and facilitating positioning of the wheelchair over the toilet.
In use, the wheelchair is normally maintained in a lowered position with the threaded rods fully retracted. In such a lowered position, a person in the wheelchair can easily fit their legs beneath a table, for example during eating at a kitchen table. The seat and upper frame can be raised by actuating the motor to turn the tubes, thereby extending the screws. Preferably, the seat can be raised at least to the height of a bed to facilitate transfer of a person between the chair and the bed. Also, in a fully raised position, a person sitting in the chair can reach shelves in a cupboard above a countertop, such as in a kitchen.